Of the games I've run that actually use saving throws I've probably run more BX than anything else. I don't come close to codifying it in any of my games but I look at the BX saving throws as kind of God's Nielsen ratings. First level you have an even chance of staying alive in most conditions but you're SOL when something supernatural comes up and, yknow, that's just the natural order that Keproth or YHWH set into the universe.
That's how it should be. You are A Dude and A Dude should not have great chances vs. dragon breath. There's nothing special about those who decide to get an axe or learn Read Languages and head out to get rich enough to never slop pigs again. If anything this is natural selection. Why should an almighty care? Fuck em, let them die.
But when someone does great things,
and I mean large or immense not super-good,
so like great atrocities even, as they go through their life,
this attracts attention.
Even from spheres that never normally paid you any heed.
And the more godly attention is focused around you, the more people like the show, the better chance it has of surviving cancellation. They're still watching to see you flame out and die horribly, like the X-Games or a monster truck rally or David Blaine or America's Funniest Videos, you're not their Chosen One or their boo. But off-the-shelf gods are often super boring so I figure they get super bored, too. The higher your level, the more interesting stuff you've done and more watchable you are and the bigger risks you're taking and the bigger the likelihood that your death is going to be hilarious.
Now this is one of those fantastic things that is modeled live at the table because there always is a pantheon corralled around your plane of existence, hanging on your fate, waiting to see what happens. It's you guys, the players and DM, and of course any passersby. You're all going to be just as excited whether the archer makes the shot or historically botches, and the higher the stakes the more you're all going to be interested. In fact if you're playing in a public place like I'm going to be doing again soon, I'd happily apply a bonus for every random dude the bedlam of play draws over the observe.
I stress again, now, that I don't formalize this. It shouldn't be overliteralized, as that shits in the metaphor's mail. It's just a way of intellectualizing the chances of survival in the face of, not risk, but the impossible. I'm stealing a line here (from +Courtney Campbell?) but every trap and catoblepas gaze and ghoul touch is a life or death roll, a moment where you should be fucked but you're somehow given an astonishing 10% chance of survival? In the face of a dragon blowing fire acid at you? That's huge. That's your Luck mechanic, people, your uncodified Fortune stat.
Now on that model your saves differed depending on what Class you played, back in the stone age when class and race were the same thing. This made sense, I think, especially from a game-first perspective, but some people just couldn't stand that first level Samwise Gamgee had a better set of default saves than first level Robin Hood, or that Conan's save improved so much faster than Merlin's. Never mind the fact that Your Character Is None Of These Characters but that's a whole other article...
When the catechism came, saving throws became mostly the province of the Class. What you did determined how fortunate you were. Well some people didn't like THAT so then you had racial bonuses, feat bonuses....Eventually you could just pile saving bonuses up like cocaine money.
Eventually you were considered to be fucking awesome enough to survive certain death by virtue of being an ADVENTURER, a manner of people above the rest. Because you were a Main Character with all associated resistances and immunities. It's more or less still that way now that 5e is out, although they've tried to slide the scale back in a lethal direction....
For XXR I lean mostly toward the Old Ways as well. I use BXish saves because they're easy to me now, with the exception of Shock Value since that's based on derived values that vary from character to character. I've thought about turning it into a flat number but I frankly like it just for the thematic elements. I am pretty forgiving with saves, though: if I have to think for more than a second about how a challenge might be represented, I'll just have them make a save vs. their death roll. There are a few tiers of awesomeness in terms of saves for Doublecrossroads, and basically whatever Classification I started from when I was working on the weird ones, that's how they save.
I'm also slowwwwwwwwwwwwwwwwwwwwwwly writing rules that treat most mechanical considerations as saves against your own values. But that's later.